The present invention relates in general to a method of and a device for producing bags and the like of a continuous thermoplastic foil shaped in the form of a hose or a partial hose. In particular, this invention relates to manufacturing methods and devices in which the hose-like foil is intermittently advanced and through a welding and cutting station where the interlocking and bottom seams are produced and simultaneously the completed individual bags are severed from the foil web. Thereafter, the welded bags are stacked along an aligning line on pins arranged in close proximity to the welding and cutting station.
From the German DE-AS No. 21 41 045, a manufacturing method is known in which, in order to provide a stack of bags or the like envelopes, which are interlocked by welding along one of their edges, the individual bags to be stacked are welded to the edge of the preceding bag by a separate welding step. For this purpose, the welding beams have a downwardly extended part serving as a stacking station. The rear side of this part, which is adverse to the welding surface, cooperates with a bag clamping bar, whereby the formed stack of bags is held between the welding beam and the clamping bar. The welding beam on the side thereof which faces the bag clamping bar is provided with welding means for producing the interlocking seam on the bag. In the stacking process, the upper part of each bag has been banded by means of an air nozzle from the front edge of the welding beam to the rear side thereof.
In further developments known for example from DE-OS No. 22 54 448 and DE-GM No. 74 34 007, the stacking station has been separated from the welding beam and is skewed in the direction of movement of the supply foil, a welding station, a cutting station, a stack interlocking station, and also a perforation station have been arranged in close sequence in this order. The tear-off perforation in the perforating station is not made in the completed stack. The aforementioned stations arranged closely one after the other define, depending on their spacing, also the distance of the bottom weld seam of each bag and the interlocking weld seam with the preceding bag on the stack, as well as the distance of the tearing perforation line the assigned parallel edge of the bag. Inasmuch as the clearance between these individual stations for welding, cutting, interlocking and perforating operations cannot fall below a limit value determined from the resistance to a displacement as well as in view of the installation of necessary driving elements and because of overheating protection of insulating layers arranged therebetween, the bags produced in this prior-art device has weld seams and perforation lines which are spaced a relatively long distance from the assigned parallel edges of the bag. As a result, a relatively large percentage of foil material is wasted.
In addition, due to the fact that the above stations employ separate welding devices for the bottom weld seams of the bags and for the interlocking weld seams, separate connections to the heating elements of the welding devices are necessary, which must be controlled to produce different welding temperatures. Consequently, the construction cost is increased.